Vitamin D

What can improve your bone health, help shield you from disease, improve muscle strength, and even make you smile?

Vitamin D to the rescue! 

We have known for ages that vitamin D is essential for strong teeth and bones, but in recent years researchers and practitioners have found that Vitamin D is important for a wide range of body systems including immunity and mental health. Vitamin D is a fat soluble vitamin which means it dissolves in fat and gets stored in fatty tissues in the body. Although it retains the vitamin label, vitamin D is now considered a multifunctional hormone not a vitamin because of its role in a wide variety of processes in the body. 

Why is vitamin D so important for bones? 

First off, vitamin D is critical for growing and maintaining healthy bones and teeth. A severe deficiency of vitamin D causes rickets in children and osteomalacia in adults. These are diseases that cause bone pain, soft, weak bones, and poor growth. In the early 1900s, vitamin D was discovered because of its ability to cure rickets. Cod liver oil was found to be a good source of this vitamin and was routinely administered to children as a preventive measure for the disease. Even though this connection between vitamin D and rickets was made so long ago, rickets is still an issue in certain populations today. 

Calcium Connection…

Sufficient levels of vitamin D are directly linked to adequate levels of calcium in the body. Calcium is a mineral needed for strong teeth and bones. Getting the calcium from the food we ingest into our bones requires absorption in the intestines. This is where vitamin D comes in. It promotes calcium absorption in the gut and helps to maintain sufficient levels of both calcium and potassium in the bloodstream. Calcium is also used in many other functions in the body. When sufficient calcium is not available for these functions, the body will pull calcium from the bones in a process called demineralization which makes them weaker. Because of its relationship with calcium, insufficient vitamin D results in weak, brittle, and even misshapen bones. By making the calcium readily available, adequate levels of vitamin D helps prevent weak bones and osteoporosis.

Beyond strong bones

Vitamin D’s ability to promote healthy bones and teeth has been its main claim to fame. But did you know, it also helps with muscle weakness, regular heart rhythms, thyroid functions, normal blood clotting, cell growth, glucose metabolism, and the immune system? In addition to these roles, it is anti-inflammatory and important for mental health. Low vitamin D levels are associated with increased symptoms of both depression and anxiety. Supplementation with vitamin D has shown to improve these conditions. On top of that, Vitamin D also plays a role in regulating cell proliferation, differentiation, and apoptosis (programmed cell death). Vitamin D is currently being researched for its role in preventing certain types of cancer. 

Vitamin D is critical in establishing a healthy immune system because of its effect on both innate and adaptive immune responses – the body’s initial broad immune response and the later more targeted response, respectively. Research indicates that low levels of vitamin D are associated with increased autoimmunity and increased susceptibility to infection. There appears to be a link between low vitamin D levels and multiple sclerosis, lupus, and diabetes. Low vitamin D levels are also associated with a greater risk of infection from upper respiratory infections, bacterial infections, and the flu. During the Covid 19 pandemic, hospitalized patients deficient in vitamin D had worse outcomes regardless of the severity of their illness.  

So how do we get vitamin D ?

The primary and likely the best source of vitamin D is the sun. When our skin is exposed to the sun’s UV rays, our bodies create a precursor to vitamin D which is then converted to an active form of the vitamin that the body can use. Exposing the face and arms to sunlight for 15 minutes 3 times per week may provide the body with sufficient vitamin D during summer months, but 2 hours may be needed in the winter months. Vitamin D is produced after exposure to UVB light and sunblock may prevent the skin from producing vitamin D so some experts advise exposing the skin to the sun without sunblock for short periods of time daily. 

Sunlight is not our only source of this micronutrient. Vitamin D occurs naturally in certain foods, has been added to other foods, and is available as a supplement. Fortifying foods with vitamin D began way back in the 1930s because of the prevalence of rickets especially in poor urban areas. The vitamin D found in both food and supplements, D2 and D3, are not active forms and must be processed by the liver and kidneys to become usable. Eating the following foods that naturally contain vitamin D or are fortified with it will help prevent deficiency.

• butter, 
• cod liver oil, 
• dandelion greens, 
• egg yolks, 
• halibut, 
• liver, 
• milk and plant based milks,
• oatmeal, 
• salmon, 
• sardines, 
• sweet potatoes, 
• tuna,
• vegetable oils, and
• herbs including alfalfa, horsetail, nettle and parsley.

How much is enough?

To address the question of how much vitamin D we need, let’s start with the recommended daily allowances (RDAs) for vitamin D. The RDAs are the same for both females and males, but do vary by general age group. IU stands for international units and 40 IUs equals 1 mcg. The RDAs established by the US Food and Nutrition Board are as follows:

0-12 months – 400 IUs

1-70 years –  600 IUs

>70 years – 800 IUs

The RDAs are based on the levels sufficient to maintain bone health and normal calcium metabolism in healthy individuals. These levels also assume that UV light exposure is minimal. Measuring levels of vitamin D available in the body is a bit tricky, but typically measuring a form of vitamin D, 25(OH)D or calcidiol, in the blood is used and is believed to show both the vitamin D produced by the body and that obtained from nutrition or supplementation. However, the  correlation between these levels and the effects on the body is not fully understood. Because vitamin D is critical to so many processes and has effects that go far beyond bone health, and because many people are deficient, many holistic and functional medical doctors suggest 1000 – 5000 IUs daily to promote health.

Remember that vitamin D is fat soluble and stored in the body, so you can get too much. The Food and Nutrition Board has set upper limits for vitamin D from food, beverages, and supplements ranging from 1000 IUs for infants to 4000 IUs for adults, although these levels can be exceeded if deficient. You do not have to worry about getting too much vitamin D from the sun because the skin will limit the amount it makes. Getting a blood test to determine vitamin D levels is advisable before supplementation. In general, people living in northern areas in the US do not get sufficient UV exposure during the winter months to generate healthy levels of vitamin D, so supplementation is advisable.

Several groups of people are at risk of vitamin D deficiency and include people who:

• Are over the age of 65 (both skin production of vitamin D and gut absorption of vitamin D becomes lower as we age)
• Are obese (vitamin D may be retained in fatty tissues and not make it into the bloodstream)
• Are taking certain medicines, such as anti-epileptic drugs that interfere with vitamin D pathways
• Have osteoporosis or thin bones
• Have limited sun exposure
• Have problems absorbing vitamins and nutrients in their intestines, such as those with ulcerative colitis, Crohn disease, or celiac disease
• Have liver or kidney problems (these organs are needed to convert vitamin D to its useable form)
• Have dark skin which reduces the vitamin D made from sun exposure.

In a Nutshell…

Vitamin D is crucial for living a healthy life. Not only is it needed for strong teeth and bones, but also for a robust immune system, healthy cells, mental health, strong muscles, healthy heart, healthy thyroid, blood sugar regulation, and blood clotting. Sunlight provides us with an easy source of this powerful micronutrient, so make sure you spend time outdoors. Because sunblock may prevent vitamin D synthesis, consider waiting several minutes before applying sunblock. Include foods from the above list in your diet and use a quality vitamin D supplement if needed. Get your vitamin D blood level tested to see if you should supplement. If you belong to a population at risk for low vitamin D, supplementation may be wise.

Get outside and soak up some sun!